Water pump bearing

ABSTRACT

A water pump bearing with a seal structure on an impeller side including a ring-shaped first seal unit having its outer circumferential portion fixed to an inner circumferential portion of an outer ring and its inner circumferential portion in sliding-contact with an outer circumferential surface of a pump shaft, and a ring-shaped second seal unit disposed axially outward from the first seal unit with its inner circumferential portion fixed to an outer circumferential portion of the pump shaft and its outer circumferential portion in sliding-contact with the outer ring.

FIELD OF THE INVENTION

[0001] The present invention relates to a water pump bearing to be usedfor a water-cooled engine of an automobile or the like.

DESCRIPTION OF THE RELATED ART

[0002] Referring to FIG. 6, in a conventional water pump for awater-cooled engine of an automobile or the like, an impeller isattached to an end portion of a pump shaft 53 and a pulley 52 isattached to the other end portion thereof respectively, so that thepulley 52 causes the impeller 51 to rotate, to thereby circulate coolingwater. For fixing such a water pump, as shown in FIG. 6, generally awater pump bearing is press-fixed in a water pump housing 50 fixed to amain body of the engine. With the water pump bearing, the pump shaft 53provided with the impeller 51 at an end portion thereof and the pulley52 at the other end portion thereofrespectively is rotatably attached toan outer ring 54 of the bearing with a rolling member 55 locatedtherebetween.

[0003] Between the outer ring 54 and the pump shaft 53, a mechanicalseal 57 is provided for sealing a space 58 between the pump housing 50and the pump shaft 53 to isolate from the impeller 51.

[0004] Also, seal structures are respectively provided at the endportions of the outer ring 54, for sealing a space therewithin. Amongthe seal structures, a seal structure 56 on the impeller side isgenerally constituted of a metal ring reinforcement and an elasticmember reinforced by the ring reinforcement.

[0005] In such water pump in the public domain, when sealing effect ofthe mechanical seal 57 is deteriorated because of chronologicaltransition etc., cooling water may penetrate from the impeller 51 sideof the seal 57 into the space 58 between the pump housing 50 and thepump shaft 53.

[0006] In addition, the seal structure 56 on the impeller side isrepeatedly heated and cooled each time the engine is started andstopped, causing repeated expansion and contraction of air inside thebearing, for which the sealing effect is prone to be damaged.

[0007] Accordingly, the cooling water that has penetrated into the space58 between the pump housing 50 and the pump shaft 53 in the abovedescribed manner, or vapor generated from heating the cooling water maypenetrate into the internal area of the bearing through the sealstructure 56.

[0008] Such penetration of moisture into the internal area of thebearing causes a breakdown of the water pump because of deterioration ofgrease filled inside the bearing or rust produced inside the bearing,shortening a life span of the water pump.

[0009] Moreover, the grease may flow out of the internal area of thebearing through the seal structure 56, at which the sealing effect of ithas been deteriorated by the aforementioned reasons. The outflow of thegrease increases friction between the rolling member 55 and the pumpshaft 53, which leads to a breakdown of the water pump bearing, andconsequently to a shorter life span of the water pump.

OBJECTS OF THE INVENTION

[0010] In view of the foregoing problems with the prior art, it is anobject of the present invention to provide a water pump bearing that canprevent penetration of cooling water or moisture into an internal areaof the water pump bearing, and outflow of grease from the internal areaof the bearing.

SUMMARY OF THE INVENTION

[0011] For achieving the object, a water pump bearing according to theinvention is constituted as follows.

[0012] The water pump bearing comprises, like conventional ones, a pumpshaft provided with an impeller at one end portion thereof and a pulleyat the other end portion thereof respectively, rotatably attached to anouter ring of the bearing with at least one rolling member locatedtherebetween, and seal structures provided at both end portions of theouter ring for sealing an internal area of the bearing.

[0013] Also, there is a seal structure on a side of the impeller, amongthe seal structures provided at both end portions of the outer ring forsealing the internal area of the bearing, comprises the followingcharacteristic constitution.

[0014] The seal structure of a first embodiment comprises a ring-shapedfirst seal unit having an outer circumferential portion fixed to aninner circumferential portion of the outer ring and an innercircumferential portion in sliding-contact with an outer circumferentialsurface of the pump shaft. As shown in FIG. 1, in the seal structure ofthe first embodiment, a ring-shaped second seal unit is disposed at anaxially outer position from the first seal unit. And, the second sealunit has its inner circumferential portion fixed to an outercircumferential portion of the pump shaft and its outer circumferentialportion in sliding-contact with the outer ring.

[0015] The first seal unit comprises a ring reinforcement and an elasticmember reinforced by the ring reinforcement. An outer circumferentialportion of the first seal unit is press-fitted in a fitting grooveformed on an inner circumferential surface of the outer ring. A portionof the elastic member further extends from an end portion of the ringreinforcement on the pump shaft side toward the pump shaft for makingsliding-contact with an outer circumferential surface of the pump shaft.That portion of the elastic member comprises a first lip portionextending diagonally in an axially inward direction to makesliding-contact with an outer circumferential surface of the pump shaft,and a second lip portion extending diagonally in an axially outwarddirection to make sliding-contact with an outer circumferential surfaceof the pump shaft.

[0016] The second unit comprises a ring reinforcement having acylindrical portion extending in an axial direction and fixed to thepump shaft and a flange portion extending from the cylindrical portiontoward the outer ring, and an elastic member reinforced by the ringreinforcement. A portion of that elastic member further extends from theouter ring side end portion of the flange portion of the ringreinforcement toward the outer ring comprises a third lip portion insliding-contact with an axially outer end face of the outer ring.

[0017] In the seal structure of a second embodiment, as shown in FIG. 2,a portion of the elastic member which constitutes the second seal unitis like the first seal structure, but a portion of that elastic memberfurther extends from the outer ring side end portion of the flangeportion of the ring reinforcement toward the outer ring furthercomprises a fourth lip portion extending diagonally in an axially inwarddirection to form a non-contact labyrinth seal portion between anaxially outer lateral face of the first seal unit.

[0018] In the seal structure of a third embodiment, as shown in FIG. 3,a ring reinforcement and an elastic member which constitute the secondseal unit are like those of the first seal structure or the second sealstructure, but a cylindrical portion of a ring reinforcement further hasa reinforcing ring extending from the cylindrical portion towardradially inner direction along an axially outer end face of the pumpshaft, and a portion of an elastic member existing at the side ofradially inner part of it and reinforced by the said reinforcing ringcomprises a fifth lip portion in sliding-contact with the axially outerend face of the pump shaft.

[0019] In the seal structure of the fourth embodiment, as shown in FIG.4, the second seal unit is like the first embodiment of a sealstructure. It comprises a ring reinforcement and an elastic memberreinforced by the ring reinforcement. The inner circumferential portionof the second seal unit is press-fitted in a fitting groove formed on anouter circumferential surface of the pump shaft. A portion of theelastic member further extends from the outer ring side end portion ofthe ring reinforcement toward the outer ring so as to form a third lipportion in sliding-contact with an axially outer end face of the outerring.

[0020] In the seal structure of the fifth embodiment, as shown in FIG.5, a portion of the elastic member constituting the second seal unit islike the fourth seal structure, but a portion of that elastic memberfurther extends from the outer ring side end portion of the ringreinforcement toward the outer ring further comprises a portionextending diagonally in an axially inward direction to form a fourth lipportion that serves as a non-contact labyrinth seal portion between anaxially outer lateral face of the first seal unit.

[0021] In a water pump bearing of the invention comprising a sealstructure of any of the first to fifth aspects on the impeller side, asone of the seal structures provided at both end portions of the outerring for sealing an internal area of the bearing, the third lip portionof the second seal unit can make sliding-contact with the axially outerend face of the outer ring that has a plain, e.g. a planar surface. Itis also possible to provide an arc-shaped chamfer portion at an innercircumferential corner (on the pump shaft side) of the axially outer endface of the outer ring, so that the third lip portion makessliding-contact with the arc-shaped chamfer portion.

[0022] According to the water pump bearing of the invention, the sealstructure on the impeller side of the seal structures provided at bothend portions of the outer ring for sealing the internal area of thebearing is comprised as follows. The structure comprises the ring-shapedfirst seal unit having its outer circumferential portion fixed to aninner circumferential portion of the outer ring and its innercircumferential portion in sliding-contact with an outer circumferentialsurface of the pump shaft, and the ring-shaped second seal unit disposedat an axially outer position from the first seal unit with its innercircumferential portion fixed to an outer circumferential portion of thepump shaft and its outer circumferential portion in sliding-contact withthe outer ring. Therefore, penetration of moisture, such as coolingwater or vapor etc., into the internal area of the bearing can beeffectively prevented, and outflow of grease from the internal area ofthe bearing can also be effectively prevented.

[0023] More specifically, even if moisture, such as water or vapor,etc., has penetrated toward the internal area of the bearing through theseal portion between the third lip portion of the second seal unit andthe axially outer end face of the outer ring, the second lip portion ofthe first seal unit, which diagonally extends in an axially outwarddirection and achieves sliding-contact with an outer circumferentialsurface of the pump shaft, prevents moisture, such as water or vapor,etc., from penetrating into the internal area of the bearing.

[0024] Also, the first lip portion of the first seal unit, whichdiagonally extends in an axially inward direction and achievessliding-contact with the outer circumferential surface of the pumpshaft, prevents grease from outflowing from the internal area of thebearing.

[0025] Further, in both of the foregoing cases, a sealed space enclosedby the first lip portion and the second lip portion of the first sealunit and the outer circumferential surface of the pump shaft caneffectively prevent penetration of moisture, such as cooling water orvapor, etc., into the internal area of the bearing, as well aspreventing outflow of grease from the internal area of the bearing.

[0026] Also, where the second unit further comprises the fourth lipportion that extends diagonally toward the outer ring and in an axiallyinward direction to form a non-contact labyrinth seal portion between anaxially outer lateral face of the first seal unit, even if moisture,such as water or vapor, etc., has penetrated toward the internal area ofthe bearing through the seal portion between the third lip portion ofthe second unit and the axially outer end face of the outer ring, thelabyrinth seal portion shakes off such moisture, thus effectivelypreventing further penetration of moisture, such as water, or vapor,etc., into the area of the bearing.

[0027] In any of the seal structures adopted in the water pump bearingof the invention, it is preferable that the ring reinforcements be madeof a corrosion-resistant material, for example stainless steel, to avoidgeneration of rust on these components. In this sense the material isnot specifically limited as long as these components are made of acorrosion-resistant material. For example, steel plated with acorrosion-resistant metal may be employed.

[0028] Also, elastic members may be of materials known in this technicalfield, such as rubber or synthetic resin.

[0029] Also, constitution, configuration and arrangement described inthe following preferred embodiments referring to the accompanyingdrawings are merely a general presentation for reasonable understandingof the invention. Therefore, it is to be understood that the inventionis not limited to the forms disclosed in the following embodiments, andthat various modifications and variations may be made within thetechnical scope of the invention as set forth in the appended claims.

BRIEF DESCRIPTIONS OF THE DRAWINGS

[0030]FIG. 1 is an enlarged fragmentary cross-sectional view of animpeller side seal structure of a water pump bearing, according to afirst embodiment of the present invention.

[0031]FIG. 2 is an enlarged fragmentary cross-sectional view of animpeller side seal structure of a water pump according to a secondembodiment of the invention.

[0032]FIG. 3 is an enlarged fragmentary cross-sectional view of animpeller side seal structure of a water pump bearing according to athird embodiment of the invention.

[0033]FIG. 4 is an enlarged fragmentary cross-sectional view of animpeller side seal structure of a water pump bearing according to afourth embodiment of the invention.

[0034]FIG. 5 is an enlarged fragmentary cross-sectional view of animpeller side seal structure of a water pump bearing according to afifth embodiment of the invention.

[0035]FIG. 6 is a partial cross-sectional view of an example of a waterpump in which a conventional water pump bearing is disposed.

DESCRIPTION OF THE PREFERRED EMOBODIMENTS

[0036] Referring to the accompanying drawings, descriptions hereunderare of preferred embodiments of seal structures adopted as a sealstructure 56 on an impeller 51 side, which is among seal structures thatare provided at both end portions of an outer ring 54 for sealing theinternal area of the bearing. These have been adapted for use in thewater pump bearing of the invention to constitute the essential part ofthe bearing. Since the portions other than the seal structures describedbelow are the same as conventional ones described referring to FIG. 6,description of such other portions is omitted. Also, identicalcomponents to those referred to in FIG. 6 that illustrates aconventional example are denoted by identical reference numerals tothose used in FIG. 6, and description thereof is omitted.

[0037]FIG. 1 shows a first embodiment of the impeller 51 side sealstructure, which among at least two seal structures provided at both endportions of the outer ring 54 of the water pump bearing of the inventionfor sealing the internal area of the bearing.

[0038] The seal structure shown in FIG. 1 comprises a ring-shaped firstseal unit 10 having an outer circumferential portion fixed to an innercircumferential portion of the outer ring 54 of the bearing and an innercircumferential portion in sliding-contact with an outer circumferentialsurface of a pump shaft 53. A ring-shaped second seal unit is disposedaxially outward of the first seal unit 10. The unit 20 has its innercircumferential portion fixed to an outer circumferential portion of thepump shaft 53 and its outer circumferential portion in sliding-contactwith the outer ring 54.

[0039] The first seal unit 10 comprises a metal ring reinforcement 11and an elastic member 12 made of an elastic material such as rubber,reinforced by the ring reinforcement 11. The outer circumferentialportion of the first seal unit 10 is press-fitted in a fitting grooveformed on an inner circumferential surface of the outer ring 54.

[0040] The elastic member 12 further extends from the pump shaft sideend portion 13 of the ring reinforcement 11 toward the pump shaft 53,thus achieving sliding-contact with an outer circumferential surface 53a of the pump shaft 53.

[0041] An inner circumferential portion, i.e. the pump shaft 53 sideportion of the elastic member 12, comprises a first lip 14 and a secondlip 15. A first lip 14 extends diagonally in an axially inward directionto make sliding-contact with an outer circumferential surface 53 a ofthe pump shaft 53. A second lip portion 15 extends diagonally in anaxially outward direction to make sliding-contact with an outercircumferential surface 53 a of the pump shaft 53.

[0042] This forms a sealed space 30 enclosed by the first lip portion 14and the second lip portion 15 of the first seal unit 10 and the outercircumferential portion 53 a of the pump shaft 53.

[0043] The second seal unit 20 comprises a metal ring reinforcement 23and an elastic member 24 made of an elastic material, such as rubber,reinforced by the ring reinforcement 23. As shown in FIG. 1, the ringreinforcement 23 comprises a cylindrical portion 21 extending in anaxial direction and fixed to the pump shaft 53 and a flange portion 22extending from the cylindrical portion 21 toward the outer ring 54.

[0044] A portion of the elastic member 24 further extends from an outerring side end portion 25 of the flange portion 22 of the ringreinforcement 23 toward the outer ring 54. That portion comprises athird lip portion 26 in sliding-contact with an axially outer end face60 of the outer ring 54, as shown in FIG. 1.

[0045] In the embodiment in FIG. 1, the outer circumferential portion ofthe first seal unit 10 is fixed to the inner circumferential portion ofthe outer ring 54 by pressing the first seal unit 10 toward an axiallyinward direction of the water pump bearing (the left side in FIG. 1), sothat a lump-shaped outer circumferential portion of the first seal unit10 is press-fitted in a fitting groove 59 formed on the innercircumferential portion of the outer ring 54. Once the outercircumferential portion of the first seal unit 10 has been fixed to theinner circumferential portion of the outer ring 54 in this way, thefirst lip portion 14 and the second lip portion 15 of the first sealunit 10 make sliding-contact with the outer circumferential surface 53 aof the pump shaft 53, defining a sealed space 30 enclosed by the firstlip portion 14, the second lip portion 15 and the outer circumferentialsurface 53 a of the pump shaft 53.

[0046] Also, in FIG. 1, the cylindrical portion 21 is fixed over thepump shaft 53 by pressing the second seal unit 20 toward an axiallyinward direction of the water pump bearing (the left side in FIG. 1).Once the inner circumferential portion of the second seal unit 20 hasbeen fixed to the outer circumferential portion of the pump shaft 53 inthis way, the third lip portion 26 achieves contact with the axiallyouter end face 60 of the outer ring 54, thus forming a seal portion.

[0047] Further, in this embodiment the elastic member 24 of the secondseal unit 20 extends to an inner circumferential edge portion of thecylindrical portion 21 of the ring reinforcement 23, forming aprojection 34. When the inner circumferential portion of the second sealunit 20 is fixed to the outer circumferential portion of the pump shaft53, this fixes the projection 34 of an elastic material with the metalouter circumferential surface 53 a of the pump shaft 53, in addition tofitting of metal materials between the metal cylindrical portion 21 andthe metal outer circumferential surface 53 a of the pump shaft 53.Therefore, sealing capacity can be improved.

[0048] When the seal structure in FIG. 1 is adopted as the impeller 51side seal structure, among seal structures provided at both end portionsof the outer ring 54 for sealing the internal area of the bearing, dualring-shaped seal units are employed at axially inner and outerpositions. One of them is a seal unit that has its outer circumferentialportion fixed to the inner circumferential portion of the outer ring 54and its inner circumferential portion in sliding-contact with the outercircumferential surface of the pump shaft 53. The other of them is aseal unit that has its inner circumferential portion fixed to the outercircumferential portion of the pump shaft 53 and its outercircumferential portion in sliding-contact with the outer ring 54.Therefore, penetration of moisture, such as cooling water or vapor,etc., into the internal area of the bearing can be effectivelyprevented, and outflow of grease from the internal area of the bearingcan also be effectively prevented.

[0049] More specifically, moisture that might penetrate into theinternal area of the bearing is blocked by the seal portion formedbetween the third lip portion 26 of the second seal unit 20 and theaxially outer end face 60 of the outer ring 54.

[0050] Further, even if moisture penetrates through the seal portionformed between the third lip portion 26 of the second seal unit 20 andthe axially outer end face 60 of the outer ring 54 toward the internalarea of the bearing, the second lip portion 15 of the first seal unit 10diagonally extending in an axially outward direction and insliding-contact with the outer circumferential surface 53 a of the pumpshaft 53 effectively prevents moisture from penetrating into theinternal area of the bearing.

[0051] Also, the first lip portion 14 of the first seal unit 10 extendsdiagonally in an axially inward direction to achieve sliding-contactwith the outer circumferential surface 53 a of the pump shaft 53 andprevent outflow of grease from the internal area of the bearing.

[0052] Further, the sealed space 30 enclosed by the first lip portion 14and the second lip portion 15 of the first seal unit 10 and the outercircumferential surface 53 a of the pump shaft 53 can effectivelyprevent penetration of moisture, such as cooling water or vapor, etc.,into the internal area of the bearing, and outflow of grease from theinternal area of the bearing.

[0053] In addition, since the projection 34 of an elastic material isprovided at the inner circumferential edge portion of the cylindricalportion 21 of the ring reinforcement 23, the projection 34 is fixed withthe metal outer circumferential surface 53 a of the pump shaft 53 oncethe inner circumferential portion of the second seal unit 20 is fixed tothe outer circumferential portion of the pump shaft 53. This effectivelyprevents generation of rust on the metal cylindrical portion 21 and themetal outer circumferential surface 53 a of the pump shaft 53.

[0054] In FIG. 1, the third lip portion 26 of the second seal unit 20 isin sliding-contact with the axially outer end face 60 of the outer ring54 that has a plain, e.g., planar surface. It may also be preferable toprovide an arc-shaped chamfer portion 61 at an inner circumferentialcorner (on the pump shaft 53 side) of the axially outer end face 60 ofthe outer ring 54, as in the embodiment in FIG. 2. Then the third lipportion 26 of the second seal unit 20 makes sliding-contact with thearc-shaped chamfer portion 61.

[0055] Also, while the flange portion 22 of the ring reinforcement 23has a straight cross-section in FIG. 1, it may be formed such that thecross section is a curved shape, as in FIG. 2.

[0056]FIG. 2 shows a second embodiment of the impeller 51 side sealstructure, which is among the at least one seal structures at both endportions of the outer ring 54 of the water pump bearing of theinvention, for sealing the internal area of the bearing.

[0057] Since the basic cofiguration and structure of FIG. 2 are similarto FIG. 1, the same reference numerals are given to components used incommon, and description thereof shall be omitted.

[0058] The embodiment in FIG. 2 differs from FIG. 1 in that a portion ofthe elastic member 24 constituting the second seal unit 20 extendsfurther from the outer ring side end portion 25 of the ringreinforcement flange portion 22 and toward the outer ring 5 furthercomprises a fourth lip portion 27 diagonally extending in an axiallyinward direction so as to form a non-contact labyrinth seal portion 28between an axially outer lateral face of the first seal unit 10.

[0059] In FIG. 2, the inner circumferential portion of the second sealunit 20 is fixed over the outer circumferential surface of the pumpshaft 53 by pressing the second seal unit 20 in an axially inwarddirection of the water pump bearing (the left side in FIG. 2). Once theinner circumferential portion of the second seal unit 20 has been fixedto the outer circumferential surface of the pump shaft 53, the third lipportion 26 contacts the arc-shaped chamfer portion 61 formed at an innercircumferential corner (on the pump shaft 53 side) of the axially outerend face 60 of the outer ring 54, thus forming a seal. Concurrently, thenot-contact labyrinth seal portion 28 is formed between a tip portion ofthe fourth lip portion 27 and the axially outer lateral face of thefirst seal unit 10.

[0060] Even if moisture has penetrated toward the internal area of thebearing through the seal portion between the third lip portion 26 of thesecond seal unit 20 and the axially outer end face 60 of the outer ring54, the labyrinth seal portion 28 in FIG. 2 shakes off such moisture,thus effectively preventing further penetration of moisture into theinternal area of the bearing. This is in addition to the effect andadvantage of the embodiment of FIG. 1.

[0061] Further, the labyrinth seal portion 28 may be formed between aflat portion of the axially outer lateral face of the first seal unit 10and the tip portion of the fourth lip portion 27 which extendsdiagonally in an axially inward direction and toward the outer ring 54,unlike the embodiment shown in FIG. 2.

[0062] However, forming a labyrinth seal portion 28 between a face 32confronting the pump shaft 53 of a bulge portion 31 of the first sealunit 10 protruding in an axially outward direction and the tip portionof the fourth lip portion 27 as shown in FIG. 2, is advantageous formore effective prevention of penetration of moisture into the internalarea of the bearing.

[0063] Further, in the embodiment of FIG. 2, it is preferable to arrangethe third lip portion 26 of the second seal unit 20 to makesliding-contact with an axially outer end face 60 of the outer ring 54that has a plain surface. In addition, the flange portion 22 of the ringreinforcement 23 may be formed to have a straight cross-section, asshown in FIG. 1.

[0064]FIG. 3 shows a third embodiment of the impeller 51 side sealstructure, which is among the at least one seal structures at both endportions of the outer ring 54 of the water pump bearing of theinvention, for sealing the internal area of the bearing.

[0065] Since the basic cofiguration and structure of FIG. 3 are similarto FIG. 2, the same reference numerals are given to components used incommon, and description thereof shall be omitted.

[0066] The embodiment in FIG. 3 differs from FIG. 2 in that acylindrical portion 21 of a ring reinforcement 23 further has areinforcing ring 35 extending from the cylindrical portion 21 towardradially inner direction along an axially outer end face of the pumpshaft 53, and a portion of an elastic member 24 existing at the side ofradially inner part of it and reinforced by the said reinforcing ring 35comprises a fifth lip portion 36 in sliding-contact with the axiallyouter end face of the pump shaft 53.

[0067] Since the fifth lip portion 36 of an elastic material is providedat the inner circumferential edge portion of the elastic member 24 insliding-contact with the axially outer end face of the pump shaft 53,fifth lip portion 36 is fixed with the axially outer end face of thepump shaft 53 once the inner circumferential portion of the second sealunit 20 is fixed to the outer circumferential portion of the pump shaft53. This can improve sealing capacity as well as this effectivelyprevents generation of rust on the metal cylindrical portion 21 and themetal outer circumferential surface 53 a of the pump shaft 53 . This isin addition to the effect and advantage of the embodiment of FIG. 2.

[0068] In the embodiment of FIG. 3, it is preferable to arrange theportion of the elastic member 20 further extends from an outer ring sideend portion of the flange portion of the ring reinforcement toward theouter ring 54 to the portion shown in FIG. 1 as it does not have thefourth lip 27.

[0069] Also, in the embodiment of FIG. 3, it is preferable to arrangethird lip portion 26 of the second seal unit 20 to make sliding-contactwith an axially outer end face 60 of the outer ring 54 that has a plainsurface. In addition, the flange portion 22 of the ring reinforcement 23may be formed to have a straight cross-section, as shown in FIG. 1.

[0070]FIG. 4 shows the fourth embodiment of the impeller 51 side sealstructure, which is one of the seal structures provided at both endportions of the outer ring 54 of the water pump bearing of the inventionfor sealing the internal area of the bearing.

[0071] Since the basic configuration and structure in FIG. 4 are similarto FIG. 1, the same reference numerals are given to components used incommon, and description thereof shall be omitted.

[0072] The embodiment in FIG. 4 shows a difference from FIG. 1 in thatthe inner circumferential portion of the second seal unit 20 ispress-fitted in a fitting groove 62 formed on the outer circumferentialsurface of the pump shaft 53.

[0073] Also, in FIG. 4, a ring reinforcement 29 of the second seal unit20 which reinforces the elastic member 24 made of an elastic material,such as rubber, is provided with a plurality of slits formed in a radialdirection and aligned in a circle at an inner circumferential portionthereof (on the pump shaft 53 side).

[0074] The inner circumferential portion of the second seal unit 20 isfixed over the outer circumferential surface of the pump shaft 53 bypressing the second seal unit 20 toward an axially inward direction ofthe water pump bearing (toward the left in FIG. 3), so that alump-shaped inner circumferential portion of the second seal unit 20 ispress-fitted in the fitting groove 62 formed on the outercircumferential surface of the pump shaft 53. And once the innercircumferential portion of the second seal unit 20 has been fixed to theouter circumferential surface of the pump shaft 53 in this way, thethird lip portion 26 achieves contact with the axially outer end face 60of the outer ring 54, thus forming a seal.

[0075] Referring to the mentioned process, since the ring reinforcement29 of the second seal unit 20 is constructed as described above, thesecond seal unit 20 can be more easily and more firmly press-fittedbecause of a resilience of the ring reinforcement 29. As a result,sealing capacity against moisture such as cooling water or vapor etc.that is going to penetrate into the internal area of the bearing can beimproved.

[0076] Also, the third lip portion 26 of the second seal unit 20 maymake sliding-contact with the arc-shaped chamfer portion 61 at an innercircumferential corner (on the side of the pump shaft 53) of the axiallyouter end face 60 of the outer ring 54 shown in FIG. 2, instead of theform in which the third lip portion 26 of the second seal unit 20 is insliding contact with the axially outer end face 60 of the outer ring 54that has a plain surface.

[0077] Other effect and advantage are similar to those described withreference to the first embodiment shown in FIG. 1.

[0078]FIG. 5 shows a fifth embodiment of the impeller 51 side sealstructure, which is one of the seal structures provided at both endportions of the outer ring 54 of the water pump bearing of the inventionfor sealing the internal area of the bearing.

[0079] Since the basic configuration and structure are similar to FIG.2, the same reference numerals are given to common components, anddescription thereof shall be omitted.

[0080]FIG. 5 differs from FIG. 2 in that the inner circumferentialportion of the second seal unit 20 is press-fitted in the fitting groove62 formed on the outer circumferential surface of the pump shaft 53.

[0081] In FIG. 5, the inner circumferential portion of the second sealunit 20 is fixed over the outer circumferential surface of the pumpshaft 53 by pressing the second seal unit 20 axially inward of the waterpump bearing (toward the left side in FIG. 5), so that a lump-shapedinner circumferential portion of the second seal unit 20 is press-fittedin the fitting groove 62 formed on the outer circumferential surface ofthe pump shaft 53. Once the inner circumferential surface of the pumpshaft 53, the third lip portion 26 contacts the axially outer end face60 of the outer ring 54 thus forming a seal portion, and the non-contactlabyrinth seal 28 is formed between a tip portion of the fourth lipportion 27 and the axially outer lateral face of the first seal unit 10.

[0082] Also, the third lip portion 26 of the second seal unit 20 maymake sliding-contact with the arc-shaped chamfer portion 61 at the innercircumferential corner (on the pump shaft 53 side) of the axially outerend face 60 of the outer ring 54 as in FIG. 2, instead of the form inwhich the third lip portion 26 of the second seal unit 20 is insliding-contact with the axially outer end face 60 of the outer ring 54that has a plain surface.

[0083] Basic effect and advantage are similar to those described withreference to the second embodiment shown in FIG. 2.

[0084] According to the invention, a water pump bearing that can preventpenetration of cooling water or moisture into an internal area of thewater pump bearing and outflow of grease from the internal area of thebearing can be obtained.

[0085] Although the present invention has been described in relation toparticular embodiments thereof, many other variations and modificationsand other uses will become apparent to those skilled in the art. It ispreferred, therefore, that the present invention be limited not by thespecific disclosure herein, but only by the appended claims.

What is claimed is:
 1. A water pump bearing, comprising; a pump shafthaving an outer circumferential surface; an outer ring around the shaftthe outer ring having an inner circumferential portion; the outer ringhaving an axial end face at a lateral side of the bearing; a rollingmember located between the outer ring and the pump shaft enablingrelative rotation between the outer ring and the pump shaft; a seal atthe shaft and the outer ring located at the axial end of the outer ringand shaped and positioned for sealing an internal area of the bearingbetween the outer ring and the shaft, the seal comprising; a ring shapedfirst seal comprising a first elastic member, and having a first outercircumferential portion fixed to the inner circumferential portion ofthe outer ring and having a first inner circumferential portion which isin sliding-contact with the outer circumferential surface of the pumpshaft; a fitting groove formed in the inner circumferential surface ofthe outer ring, the first outer circumferential portion of the firstseal bearing fitted in the fitting groove in the inner circumferentialsurface of the outer ring; a first portion of the first elastic memberextending toward the pump shaft for making sliding-contact with theouter circumferential surface of the pump shaft, the first portion ofthe first elastic member comprising a first lip extending diagonally andaxially inward to make sliding-contact with the outer circumferentialsurface of the pump shaft and also comprising a second lip extendingdiagonally and axially outward to also make sliding-contact with theouter circumferential surface of the pump shaft, whereby the first andthe second lips are spaced apart along and contact the pump shaft; aring-shaped second seal disposed axially outward of the first seal andnearer to the axial end of the outer ring than the first seal, thesecond seal having a second inner circumferential portion fixed to theouter circumferential portion of the pump shaft and having a secondouter circumferential portion in sliding-contact with the outer ring;the second seal comprising a cylindrical portion extending in an axialdirection and fixed to the pump shaft and further comprising a flangeextending radially from the cylindrical portion and toward the outerring; a portion of the second seal flange extending toward the outerring and the flange portion comprises a third lip in sliding-contactwith the axially outer end face of the outer ring.
 2. The bearing ofclaim 1, wherein the first seal comprises a first ring reinforcement forthe elastic member located radially outward from the pump shaft andhaving an inner end; the first portion of the first elastic memberextending from the inner end of the first ring reinforcement and on thepump shaft side of the elastic member.
 3. The bearing of claim 2,wherein the second seal comprises a second elastic member extending fromthe pump shaft into sliding-contact with the outer ring; a portion ofthe elastic member extending axially outward and being insliding-contact with the axially outer end face of the outer ring, and asecond ring reinforcement for the second elastic member, the second ringreinforcement having a cylindrical portion, and a ring portion extendingfrom the cylindrical portion radially inward along an axially outer endface of the pump shaft, the second elastic member having a radialportion overlying the radially inner face of the ring portion andreinforced thereby, the radial portion terminating at its radially innerend in a lip portion in sliding-contact with the axially outer end faceof the pump shaft.
 4. The bearing of claim 3, further comprising asecond ring reinforcement for reinforcing the second elastic member andhaving a cylindrical portion extending in an axial direction, whereinthe second ring reinforcement is fixed to the pump shaft, the secondring reinforcement further comprises a second flange portion extendingfrom the cylindrical portion thereof toward the outer ring, the flangeportion of the second elastic member extending axially outward beyondthe second ring reinforcement.
 5. The bearing of claim 1, wherein thesecond seal comprises a second elastic member extending from the pumpshaft into sliding-contact with the outer ring; a portion of the elasticmember extending axially outward and being in sliding-contact with theaxially outer end face of the outer ring.
 6. The bearing of claim 5,further comprising a second ring reinforcement for reinforcing thesecond elastic member and having a cylindrical portion extending in anaxial direction, wherein the second ring reinforcement is fixed to thepump shaft, the second ring reinforcement further comprises a secondflange portion extending from the cylindrical portion thereof toward theouter ring, the flange portion of the second elastic member extendingaxially outward beyond the second ring reinforcement.
 7. The water pumpbearing of claim 5, wherein the portion of the second elastic memberextending toward the outer ring further comprises a fourth lip extendingdiagonally, radially outwardly and also axially inward to form with anaxially outer, lateral face of the first seal, a non-contact labyrinthseal between the first and second seals.
 8. The bearing of claim 5,further comprising a fitting groove formed on an outer circumferentialsurface of the pump shaft; the inner circumferential portion of thesecond seal being press fit in the groove; and the portion of the secondelastic member further extending toward the outer ring thereby forming athird lip in sliding-contact with the axially outer end face of theouter ring.
 9. The bearing of claim 6, wherein the second elastic memberextends from the outer ring side end portion of the second ringreinforcement.
 10. The bearing of claim 9, wherein the portion of thesecond elastic member extending toward the outer ring further comprisesa fourth lip extending diagonally, radially outwardly and also axiallyinward to form with an axially outer, lateral face of the first seal, anon-contact labyrinth seal between the first and second seals.
 11. Thebearing of claim 1, wherein the pump shaft has an end with an impellerthereon and the pump shaft has a pulley thereon spaced from theimpeller; and the seal being at the impeller side of the shaft.
 12. Thebearing of claim 11, wherein the shaft has end portions and the impelleris at one of the end portions of the shaft and the pulley is at theother end portion of the shaft; a further seal structure at the pulleyend of the outer ring for sealing an internal area of the bearingbetween the seal at the pulley end of the shaft and the seal at theimpeller end of the shaft.